Wing Roots and whatnots
Just a bit of ancient history for you - but the original intent was to use GE engines on the MRA4 which would have more or less fitted into the original bays, leaving only a new outer wing. At the 11th hour of the proposal (I'm talking mid 1996) the Company received the edict of 'if you can't fit RR engines you can't have the deal' - a last minute political/commercial decision, but one which the Company took on and underestimated as a much greater level of wing design was needed, including all of the inherent intake issues around using pod-designed engines onboard, which took much longer than originally planned to reolve. It also left the ' how to fix a CAD wing to a bespoke wing box' question open until well into production and the actual items were available.
One for the history books.